The present invention relates to absorbent articles which are primarily designed to receive and retain bodily discharges such as urine. Such articles are disposable hygiene articles like baby diapers, training pants, adult incontinence articles and the like.
Absorbent Articles for receiving and retaining bodily discharges such as urine or feces such as disposable diapers, training pants, adult incontinence articles are well known in the art, and significant effort has been spent against improving their performance. The ability to provide better performing absorbent articles such as diapers has been contingent on the ability to develop relatively thin absorbent cores or structures that can acquire and store large quantities of discharged body fluids, in particular urine.
In this regard, the use of certain absorbent polymers often referred to as xe2x80x9chydrogels,xe2x80x9d xe2x80x9csuperabsorbentsxe2x80x9d or xe2x80x9chydrocolloidxe2x80x9d or xe2x80x9chydrogel formingxe2x80x9d material has been particularly important. See, for example, U.S. Pat. No. 3,699,103 (Harper et al), issued Jun. 13, 1972, and U.S. Pat. No. 3,770,731 (Harmon), issued Jun. 20, 1972, that disclose the use of such absorbent polymers (hereafter xe2x80x9chydrogel-forming absorbent polymersxe2x80x9d) in absorbent articles. Indeed, the development of thinner diapers has been the direct consequence of thinner absorbent cores that take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large quantities of discharged body fluids, typically when used in combination with a fibrous matrix. See, for example, U.S. Pat. No. 4,673,402 (Weisman et al), issued Jun. 16, 1987 and U.S. Pat. No. 4,935,022 (Lash et al), issued Jun. 19, 1990, that disclose dual-layer core structures comprising a fibrous matrix and hydrogel-forming absorbent polymers useful in fashioning thin, compact, nonbulky diapers. See also, U.S. Pat. No. 5,562,646 (Goldman et al.), issued Oct. 8, 1996 and U.S. Pat. No. 5,599,335 (Goldman et al.), issued Feb. 4, 1997, both of which relate to absorbent cores comprising regions of high concentrations of hydrogel-forming polymer, where the polymer forms a gel-continuous fluid transportation zone upon swelling.
In addition or alternatively to the use of hydrogel-forming absorbent polymers as the primary component in absorbent article storage structures, the use of polymeric foam materials derived from high internal phase water-in-oil emulsions (xe2x80x9cHIPEsxe2x80x9d) has been identified. See, e.g., U.S. Pat. No. 5,260,345 (DesMarais et al.), issued Nov. 9, 1993, U.S. Pat. No. 5,387,207 (Dyer et al.) issued Feb. 7, 1995, and U.S. Pat. No. 5,560,222 (DesMarais et al.), issued Jul. 22, 1997.
Also the application of such materials in absorbent structures and absorbent articles focused on storage of the fluids within the structure, often considering comfort aspects like thinness of the structure, such as disclosed U.S. Pat. No. 4,610,678 entitled xe2x80x9cHigh-Density Absorbent Structuresxe2x80x9d issued to Weisman et al. on Sep. 9, 1986; U.S. Pat. No. 4,673,402 entitled xe2x80x9cAbsorbent Articles With Dual-Layered Coresxe2x80x9d issued to Weisman et al. on Jun. 16, 1987; U.S. Pat. No. 4,888,231 entitled xe2x80x9cAbsorbent Core Having A Dusting Layerxe2x80x9d issued to Angstadt on Dec. 19, 1989; EP-A-0 640 330 of Bewick-Sonntag et al.; U.S. Pat. No. 5,180,622 (Berg et al.); U.S. Pat. No. 5,102,597 (Roe et al.); U.S. Pat. No. 5,387,207 (LaVon); EP-A-774.242; or EP-A- 0.797.968 and EP-A-0.810.078.
Further disclosure is made of structures having a low capacity in the regions between the legs of the wearer such as in PCT application U.S. 97/05046, filed on Mar. 27, 1997, relating to the movement of fluid through certain regions of the article comprising materials having good acquisition and distribution properties to other regions comprising materials having specific liquid storage capabilities.
Whilst such materials have been designed with capillary transport mechanisms in mind, thus aiming at positioning materials with smaller capillaries and/or increased hydrophilicity closer to the ultimate storage material, and materials with larger pores and less hydrophilicity closer to the loading zone, it has not been recognized, that acquisition/distribution materials have the tendency to not only transport the fluid, but also to retain the liquid, which can result under specific conditions to undesired effects, such as rewet or reduced fluid acquisition and/or distribution performance, which is particularly pronounced for acquisition/distribution materials being designed to balance acquisition and distribution properties.
Accordingly, it is an object of the present invention to provide an absorbent structure, which has an improved balance of the fluid handling properties such that well performing acquisition/distribution materials or members can be dewatered efficiently by the storage materials or members.
It is a further object of the present invention where this is achieved by fluid storage materials or members having a high liquid suction capability.
It is an even further object of the present invention, to provide an absorbent storage material or member having a high capillary suction capacity, wherein the absorbent storage material or member comprises hydrogel-forming absorbent polymer.
It is as further object of the invention, to select combinations of suitable materials for such absorbent structures by applying the capsorption test as laid out hereinafter.
The present invention relates to absorbent structures for use in absorbent articles, comprising a first region for acquisition/distribution of fluid and a second region for storage of fluid. The first region comprises materials, which may have a relatively high capillary desorption pressure, as the second region comprises materials or members exhibiting a sufficiently high capillary absorption pressure so as to still efficiently drain the first region.
The invention aims at defining the absorption properties of the storage absorbent member in combination with the desorption properties of the acquisition/distribution member such that the acquisition/distribution members are still effectively and efficiently dewatered by the storage absorbent member, whereby the fluid acquisition/distribution materials still exhibit good fluid distribution properties and thus have comparatively high capillary pressures.
In one aspect, the present invention comprises an absorbent structure comprising a first region and a second region in liquid communication with the first region whereby the first region comprises material having a Capillary Sorption Desorption Height corresponding to a capacity of 90% of the maximum capacity at 0 cm height (CSDH 90) of more than 40 cm and the second region comprises material which satisfies at least one of following requirements:
(a) a Capillary Sorption Absorption Capacity at 35 cm (CSAC 35) of at least 15 g/g in the capsorption test; and/or
(b) a Capillary Sorption Absorption Capacity at 0 cm (CSAC 0) of at least 15 g/g in the capsorption test and an Capillary Sorption Absorption Efficiency at 40 cm (CSAE 40) of at least 55%; and/or
(c) a Capillary Sorption Absorption Height at 50% of its capacity at 0 cm absorption height (CSAH 50) of at least 35 cm in the capsorption test.
In a preferred embodiment, the second region comprises material having a CSAC at 40 cm (CSAC 40) of at least 20 g/g, or alternatively at least 15 g/g at the actual CSDH 90 of the first material.
In another preferred embodiment, the second region comprises material having a CSAC 0 of at least 20 g/g, preferably more than 25 g/g, and even more preferably at least 35 g/g, when having a CSAE 40 of at least 50%.
Alternatively, the second region can comprise material having CASC 0 of at least 15 g/g and a CSAE of at least 55% at the actual CSDH 90 of the first material.
In a further, preferred embodiment, the second region comprises material having a CSAC 0 of at least 15 g/g and a CSAE 40 of at least 65%.
In another preferred embodiment, the second region comprises material having a Capillary Sorption Absorption Height at 50% of its capacity at 0 cm absorption height (CSAH 50) of at least 45 cm, preferably at least 60 cm, and even more preferably at least 80 cm.
In another alternative aspect, the first region comprises material having a CSDH 90 of more than 100 cm and the second region comprises material which satisfies at least one of following requirements:
(a) a CSAC 100 of at least 5 g/g;
(b) a CSAC 0 of at least 15 g/g and a CSAE 100 of at least 25%;
(c) a CSAH 50 of at least 35 cm.
In a preferred embodiment of this aspect, the second region comprises material having an CSAC 0 of at least 20 g/g, preferably at least 25 g/g, and even more preferably at least 35 g/g, whereby the CSAE {60 cm} is at least 50%.
In an alternative aspect of this embodiment, the second region comprises material having CSAC 0 of at least 15 g/g and a CSAE at the actual CSDH 90 of the first material of at least 50%.
In a further aspect of the present invention, the second region comprises material having a CSAH 50 of at least 45 cm, preferably of at least 60 cm, and even more preferably of at least 80 cm.
In yet another aspect of the invention, the absorbent structure comprises a first region and a second region wherein the first region comprises material having a CSDH 80 of more than 35 cm and the second region comprises material which satisfies at least one of following requirements:
(a) an absorption capacity of at least 15 g/g at 35 cm in the capsorption test; and/or
(b) an absorption capacity of at least 15 g/g at 0 cm in the capsorption test and an absorption efficiency of at least 50% at 35 cm; and/or
(c) a Capillary Sorption Absorption height at 50% of its capacity at 0 cm absorption height (CSAH 50) of at least 35 cm in the capsorption test.
In a preferred embodiment of this aspect, the second region comprises material having an absorption capacity of at least 18 g/g at 35 cm in the capsorption test, preferably of at least 21 g/g at 35 cm in the capsorption test, and even more preferably at least 30 g/g at 35 cm in the capsorption test.
In an alternative embodiment of this aspect, the second region comprises material having an absorption capacity of at least 15 g/g at the actual CSDH 80 of the first material.
In a preferred embodiment of this aspect, the second region comprises material having an absorption capacity of at least 20 g/g, preferably at least 25 g/g, even more preferably of at least 35 g/g at 0 cm in the capsorption test and an absorption efficiency of at least 50% at 35 cm.
In an alternative to this embodiment, the second region comprises material having an absorption capacity of at least 15 g/g at 0 cm in the capsorption test and an absorption efficiency of at least 60%, even more preferably of at least 85 % at 35 cm.
Alternatively, the second region comprises material having an absorption capacity of at least 15 g/g at 0 cm in the capsorption test and an absorption efficiency of at least 50% at the actual CSDH 80 of the first material.
In yet another preferred embodiment, the second region comprises material having a Capillary Sorption Absorption height at 50% of its capacity at 0 cm absorption height (CSAH 50) of at least 45 cm, even more preferably of at least 60, and most preferably of at least 80 cm in the capsorption test.
In yet another aspect of the present invention, the first region comprises material having a CSDH 80 of more than 60 cm and the second region comprises material which satisfies at least one of following requirements:
(a) a CSAC 60 of at least 11 g/g;
(b) a CSAC 0 of at least 15 g/g and a CSAE 60 of at least 50%;
(c) a CSAH 50 of at least 35 cm.
In a preferred embodiment of this aspect, the second region comprises material having a CSAC at the actual CSDH 80 of the first material of at least 11 g/g.
In another embodiment of this aspect, the second region comprises material having CSAC 0 of at least 20 g/g, preferably more than at least 25 g/g, even more preferably more than at least 35 g/g and CSAE 60 of at least 50%.
In an alternative embodiment of this aspect, the second region comprises material having CSAC 0 of at least 15 g/g and CSAE at the actual CSDH 80 of the first material of at least 50%.
In a further embodiment of this aspect, the second region comprises material having a CSAH 50 of at least 45 cm, preferably more than 60 cm, even more preferably more than 80 cm.
In yet another aspect the present invention is concerned with an absorbent structure, wherein the first region comprises material having a CSDH 80 of more than 90 cm, and the second region comprises material which satisfies at least one of following requirements:
(a) a CSAC 90 of at least 8.5 g/g;
(b) a CSAC 0 of at least 15 g/g and CSAE 90 of at least 20%;
(c) a CSAH 50 of at least 45 cm.
In a preferred embodiment of this aspect, the second region comprises material having a CSAC at the actual CSDH 80 of the first material of at least 8.5 g/g.
In a further preferred embodiment of this aspect, the second region comprises material having a CSAC 0 of at least 20 g/g, preferably more than 25 g/g, even more preferably more than 35 g/g and a CSAE 60 of at least 50%.
In an alternative embodiment of this aspect, the second region comprises material having a CSAC 0 of at least 15 g/g and a CSAE at the actual CSDH 80 of the first material of at least 20%.
In an even further preferred embodiment of this aspect, the second region comprises material having a CSAH 50 of at least 45 cm, more preferably of at least 60 cm, even more preferably of at least 80 cm.